Quantitative tissue analyses of prostate cancer foci in an unselected cystoprostatectomy series.	What's known on the subject? and What does the study add? Much of our understanding of the pathological basis of prostate cancer comes from our analysis of radical prostatectomy specimens. Prostate cancer diagnosed by transrectal ultrasonography-guided biopsy is more likely to be posterior and basal in orientation rather than anterior or apical. Quantitative tissue analyses have not been undertaken both with details and in an unselected population, e.g. prostate specimens from autopsy cystoprostatectomy series from bladder cancer. Quantitative tissue analysis of incidentally detected prostate cancer such as largest cancer surface area, volume, site of origin, multifocality and laterality could be of paramount importance when trying to understand the findings of screen-detected programmes and focal therapy. Cancers were found in 30% of prostates. In the 96 prostates, 215 cancer foci were identified (mean 2.24). Prostate cancer was multifocal in 60% and bilateral in 80% of cases. The site of origin was in the peripheral and transition zone (TZ) in 75% and 25%, respectively. Overall, 90% of cancer foci were clinically insignificant with volume of <0.5 mL and no grades 4-5. In all, 75% of the cancer foci were in the peripheral zone, the remainder were within the TZ. One third of cancer foci were anteriorly located beyond the area sampled by posterior biopsies. One fifth of cancer foci were ≤ 6 mm of the apex. OBJECTIVE: • To describe multifocality, volume and location of prostate cancers incidentally found in cystoprostatectomy specimens. Quantitative tissue analysis of prostate cancer in a population free of the evaluation bias associated with prostate-specific antigen level and biopsy is important as some men are likely to be offered tissue-preserving therapeutic strategies in the future. PATIENTS AND METHODS: • Cystoprostatectomy specimens for bladder cancer from 345 consecutive patients without clinically manifest prostate cancer were included. • Cancers were found in 104/345 (30%) of prostates. Cases with largest cancer >2 mL (eight patients) were excluded from morphometric study. Quantitative tissue analysis of 3-mm step-sectioned glands included largest cancer surface area, volume, site of origin, multifocality and laterality. RESULTS: • In the 96 prostates, 215 cancer foci were identified (mean 2.24). Prostate cancer was multifocal in 58% and bilateral in 79% of cases. • Of the 215 cancers, 90% were <0.5 mL and 79% <0.2 mL. Overall, 88% of cancer foci were clinically insignificant with a volume of <0.5 mL and no grades 4-5. • In all, 75% of the cancer foci were in the peripheral zone, the remainder were within the transition zone. • One third of cancer foci were anteriorly located beyond the area sampled by posterior biopsies. One fifth of cancer foci were ≤ 6 mm of the apex. • Limitations include the fact that cystoprostatectomy cancer foci are at an earlier stage than screened-detected cancers. CONCLUSION: • This detailed morphometric analysis of prostate cancer foci in a population that is free from the selection bias associated with screening can help inform our diagnostic and treatment strategies.	bladder